Video is normally a sequence of images, e.g., video frames. Digital television commonly refers to the digital representation of a rapid sequence of digitized photographic images, e.g., video, or parts thereof in synchronization with one or more digitized audio streams. The streams may be broadcast, as with live programming and many television programs, or played back from a digital recording on a per user basis as with the current Video On Demand (VOD) technology.
The storage of digital television images has converged on the use of the Motion Picture Expert Group (MPEG)'s standards. The standardization allowed for tremendous industry growth in the sale and distribution of digital television.
When digital television is distributed there is often a need to inject advertisements periodically. It is also necessary to inject different advertisements to different viewers as some advertisements may not be geographically relevant to some groups. E.g. advertisements for an automotive shop that is 900 miles away. In order to not have to manually stop the transmission of the primary video, play the advertisement, and then restart the primary video, a mechanism known as a playlist has evolved.
Prior to transmitting video content to a given geographic area, the primary video content will be sectioned in locations where advertisements wish to be shown. The location of each section is then placed in an array with the locations of the desired advertising video inserted between the locations of sections of primary content. The entire array is then sent to a video server which transmits the pieces of content in order. The end effect is that the viewer of the program experiences a seamless presentation of video with interspersed advertisements. One can see that this mechanism affords great flexibility as the location description for different advertisements may be swapped out each time the video is played or when it needs to be sent to geographically distant locations.
When video content is distributed via an MPEG stream or an IP encapsulated MPEG stream, it is often referred to as streaming media. The data that is the digital representation of the television image is often referred to as digital content or digital media. In order to protect copyright owners, various techniques for the encryption, watermarking, or fingerprinting of digital media have come into play. Collectively, these technologies are called Digital Rights Management (DRM) mechanisms.
Digital encryption is a process in which the series of numbers that make up the digital television content, e.g., pixel values used to represent a frame, are run through an encryption program. The encryption is such that the receiver of the data has access to the encryption key and may decrypt the content so that it may be viewed.
Along with digital encryption, industry has developed various methods to identify a copyrighted work by numerical analysis of the content. Developers have invented numerous mechanisms to extract the unique characteristics of the content such that their algorithms produce a unique digital signature for each different piece of content. The unique digital signature is often referred to as a digital fingerprint.
Digital watermarking embeds a unique identifier within digital content. Very elaborate mechanisms have evolved including those that modify the compression coefficients of the digital content or even modifying the last few significant bits of the individual frames such that they contain sequences of identifiable numbers. Some watermarking techniques alter pixel values of images providing luminance and/or chrominance information thereby slightly altering an image in a manner that is difficult or impossible to detect with the naked eye but which can be detected and interpreted as a numerical value or sequence of values from digital analysis of the image data.
One issue with the application of digital watermarks is the need for enormous computational resources in order to add the watermark in such a fashion so that it goes undetected by those who wish to defeat it. For example, to embed a number within an image as minor image luminescence changes within the horizontal and vertical confines of the image may require the complete decoding of the image, the application of a transform used to introduce the desired watermark, and the re-encoding of the content on a frame by frame basis. When streaming thousands of videos per day, the cost of the watermarking equipment which would be required to watermarking individual frames of each video stream, by altering image content within a frame in real time, can become exorbitant.
In view of the above discussion, it should be appreciated that there is a need for improved methods and apparatus for introducing information through the use of watermarks into video streams. It should be appreciated that there could be significant cost savings and reductions in hardware requirements if methods and/or apparatus could be developed which would avoid the need for altering image content, e.g., frames, for watermarking purposes at the time the frames are streamed. While not necessary for all embodiments, it would be highly desirable if watermarking equipment used to alter images, e.g., frames, was not required at individual distribution sites but could be located at a centralized or regional location used to supply content to content stores from which content could be streamed, e.g., on demand.